In recent years, it has become increasingly important to reduce the use of mercury in lighting applications because of environmental concerns related to the disposal of the mercury containing lamps. Light sources using mercury-free rare gas discharges could provide a potential solution to the disposal problem if these light sources could be adapted to meet the performance of traditional light sources such as fluorescent lighting. However, conventional fluorescent lamp phosphors which are optimized for use with low pressure mercury discharges exhibit disappointingly low levels of performance when used with rare gas discharges which emit in the vacuum ultraviolet (VUV) region of the electromagnetic spectrum. For example, europium activated yttrium oxide (YOE) phosphor, Y.sub.2 O.sub.3 :Eu, has a quantum efficiency of about 95% when excited with the 254 nm UV radiation from a mercury discharge (QE.sub.Hg .apprxeq.95%). The quantum efficiency of the same phosphor drops precipitously as the excitation source enters the vacuum ultraviolet region of the electromagnetic spectrum. Specifically, the quantum efficiency is only about 65% when excited by the 172 nm VUV radiation emitted by a xenon excimer discharge (QE.sub.Xe .apprxeq.65%). Thus, it would be an advantage to improve the performance of conventional phosphors under VUV excitation for use with rare gas discharges.